1. Field of the Invention
The present invention relates generally to fabricated energy absorbing members and inserts and the methods for making them. In a preferred embodiment, the invention describes a module which is useful for absorbing energy during a vehicular crash and thus is used as an energy absorbent insert for certain highway crash cushions.
2. Description of the Related Art
Numerous materials are known which are used in crash barriers or vehicle collision absorption systems for the absorption or dissipation of energy from vehicle collisions. These materials are usually small, items or materials, such as Styrofoam peanuts, sand and other forms of packing, which can be placed into a compartment or chamber to be crushed or displaced. Unfortunately, the use of currently available fillers sometimes causes non-uniform resistances to crushing. These non-uniform results are usually due to variances in packing procedures, manufacturing procedures, or variances in the amount and types of fillers used.
Some prefabricated objects are known which provide a member of relatively fixed size and crush resistance. An example is the prefabricated plastic barrels currently used for roadwork.
Some devices, however, require smaller prefabricated inserts which can be replaced after use. Examples of such devices are guardrail end treatments described in further detail in U.S. Pat. No. 5,391,016, entitled "Metal Beam Rail Terminal" issued to Ivey et al. and assigned to the assignee of the present invention. That patent is hereby incorporated by reference. These telescoping tube-type devices, in general, use two or more longitudinal segments which are nested within one another so that one of the segments is telescopically received within the other in response to an impact at the axial end of the device. Currently, prefabricated plastic rods or cylinders are purchased and used to provide a crushable filler or insert that is placed within the larger segment and crushed by telescopic movement of the smaller segment. It is intended that the plastic rod will crush along its length as the collision progresses, thus providing a relatively uniform and constant resistance throughout the duration of the impact and dissipating the crash energy in a controlled manner. Unfortunately, it is usually necessary to modify the plastic rods, as described in U.S. Pat. No. 5,391,016 by placing notches in the ends and then placing end caps over the ends in order to make them crush more easily. This means tools and extra components are needed to so modify the plastic rods. Further, the plastic rods are subject to manufacturing defects and variances which may affect their crush resistance. In extreme cold, the plastic becomes brittle and may tend to shatter all at once rather than be crushed along its length. In this case, the energy of the collision is not dissipated in a controlled fashion.
It would be desirable, then to have a prefabricated insert which requires no additional components, produces reliably consistent crush resistances along its length over a range of temperatures and is easy and inexpensive to produce. The present invention addresses the problems inherent in the prior art.